It's time to listen to your heart on Let's Dive In! Phil and Julie are talking about this amazing muscle. Scientist Julie Gould is here to tell you a bit more too...

Hi everyone, in this episode Phil and I try to answer the question: How does the heart pump?

First of all: why does it pump? Well, the hearts' main role is to push blood around your body. It pushed blood to the lungs to collect oxygen from the air we breathe, and it pushed blood to the rest of the body to deliver that oxygen so that our bodies can function.

The heart muscle is an amazing thing – and the muscle itself is actually very different to any other muscles in your body. Most muscles in your body receive signals from your brain telling them what to do. But the heart is different – the muscle has a special name: the cardiac muscle, and it’s got these special cells in it called pacemaker cells that do this instead. The pacemaker cells tell the heart to contract (squeeze) and relax (...relax!), which pushed blood around your body! And these special cells allow the heart to do this by itself… until it doesn’t. Let’s hope that this won’t happen any time soon!

I bet your next question is: so doesn’t the heart get tired, pumping blood around the body all the time?

The answer to that is no, too! It can keep going and going and going….


Can you imagine if your other muscles could do that? Let’s do an experiment where we try to see how long you can keep your hand pumping like the heart pumps blood. Let’s pretend your hand is your heart (actually, when balled into fists, your hands are about the same size and shape as the heart in your chest, so this is a good example!).

What you need:
Your hand
A stopwatch

What to do:
Hold your arm out in front of you
Open your hand up like a star
Close your hand into a fist
Repeat as fast as you can for 30 seconds.

Ready? GO!

How does your hand feel after that? Ready to just keep going? I thought not! But if your hand was made out of the same cardiac muscle as your heart, it could. Amazing!

Next question: What affects how quickly it beats?

Well, our mini scientists told us that they thought the heart beats because of exercise and emotions. Now, it doesn’t beat because of these things, but they do influence how quickly or slowly the heart beats.

If you go to do some exercise, your body will need more oxygen to get to the muscles, so you can do the exercise – so the heart pumps faster to get it there. The opposite happens when you rest: your body doesn’t need as much, so the heart slows down, and effectively rests too.

Phil and I talk about this and why it’s important for athletes, and we do a little experiment to measure resting heart rate. Why not have a listen to the episode to find out how you can do this too? And don’t forget to subscribe to make sure you don’t miss any other episodes!

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And if you have any questions you think we should gab about in future (now that we know where our voices come from) email